Hitherto, a large number of stereo signal processing apparatuses that suppress, based on a stereo signal in which vocals are located in the center, audio components of the vocals included in the stereo signal have been devised. For example, a vocal signal removing apparatus that subtracts a right-channel signal from a left-channel signal to remove vocal signals of the same phase and the same level included in both channels has been proposed (see, for example, PTL 1).